In the field of plastic surgery, it has become a frequent practice to implant a prosthesis in the area of the female breast for reconstruction or augmentation. In the case of reconstruction, cancerous, pre-cancerous or other abnormal or damaged tissue has been removed. This creates a void where the tissue has been removed. A prosthesis may then be inserted through an incision to fill this void. The prosthesis then becomes a permanent replacement for the damaged tissue which has been removed, and its purpose is to restore the body contour to its original configuration. The prosthesis then furnishes support for the surrounding body tissue and organs to preserve as closely as possible the original appearance of the body.
Skin and its subcutaneous tissue can be greatly expanded in area if the expansion is accomplished gradually. The extension of the skin over the pregnant female's abdomen is one example. A tissue expander is a device designed to be implanted beneath the skin then inflated to stretch the overlying skin and subcutaneous tissues. One use of such tissue expanders is to generate an increased surface area of skin to be used for grafting or reconstruction. Another use is to slowly expand the overlying skin to create a pocket beneath the skin and subcutaneous tissue to receive a permanent prosthesis such as a mammary implant.
Both mammary prostheses and tissue expanders have the common property that they have an outer resilient, stretchable membrane which encloses a space filled with a fluid or gel. The outer membrane must be stretchable to accommodate filling the implant with increasing amounts of fluid. At the same time, the outer membrane must be tough and resistant to tearing as the implant is expanded.
Other implantable medical devices such as transcutaneous catheters, artificial hearts, left ventricle assist devices have some of the common properties of mammary prostheses and tissue expanders discussed above.
Medical implants such as the above have generally been manufactured by applying a fluid layer of a resilient, stretchable material such as silicone rubber to a mandrel or mold, then allowing the silicone rubber to cure or harden on the mandrel. The implant is then removed from the mandrel. However, none of the earlier methods of manufacture take advantage of the structural engineering principle of multiple, multi-directional layers.
It is the intent of the present invention to provide a novel manufacturing method for a layered implant and a layered implant with the layers crossing each other at an angle, thereby providing increased strength and performance.